1. Field of the Invention
The present invention relates to electronics, and, in particular, to source follower circuits.
2. Description of the Related Art
Source followers are used to buffer signals and provide low output impedance to drive resistive loads. Traditional source followers have load drive capability limited to the quiescent current in the buffer. In addition, traditional source followers require too much power for many applications.
To reduce power dissipation (and area) required to reach a given output resistance, a super source follower configuration is sometimes used. See P. R. Gray, P. J. Hurst, S. H. Lewis, and R. G. Meyer, Analysis and Design of Analog Integrated Circuits, 4th ed., John Wiley & Sons, Inc., New York, 2001, pp. 213–215, the teachings of which are incorporated herein by reference. Unfortunately, the PMOS boost of this solution is too slow for many applications.
U.S. Patent Publication No. 2002/0175761 A1 (Bach et al.), the teachings of which are incorporated herein by reference, describes a PMOS version of a folded source follower. Unfortunately, this PMOS super source follower is also too slow for many applications.